The present invention relates to enhanced efficacy antiperspirant compositions containing a strontium salt and/or a calcium salt.
Enhanced efficacy aluminum and aluminum-zirconium antiperspirant salts are well known and are described, for example, in GB 2,048,229 and U.S. Pat. No. 4,775,528. These salts are generally made by heat treating a relatively dilute solution of the salt (e.g., about 10% by weight) to increase its HPLC peak 4 to peak 3 ratio, then spray drying to a powder. These salts typically have an HPLC peak 4 to peak 3 area ratio of 0.7 or higher, with at least 70% of the aluminum contained in said peaks. However, these enhanced salts are also known to rapidly revert back to their non-enhanced state (for example, as evidenced by an HPLC peak 4 to peak 3 area ratio of 0.3 or less) in aqueous solution, particularly at concentrations greater than 20%. Consequently, the enhanced antiperspirant salts are generally only available in powder form. Moreover, the enhanced salts are generally only formulated into finished formulations as suspended powders in order to retain their enhanced efficacy.
In U.S. Pat. No. 6,042,816, there are described enhanced efficacy antiperspirant salts (with peak 4:3>0.5) that are stable in aqueous solution. These salts include a soluble calcium salt such as calcium chloride and a soluble amino acid such as glycine. Typically, these salts have a Ca:Al+Zr weight ratio of about 1:1 to about 1:28 and an amino acid:Al+Zr weight ratio of about 2:1 to about 1:20. Because these salts retain their enhanced efficacy in aqueous solution (as evidenced by retention of their high peak 4:3 ratio), they have an advantage over conventional enhanced efficacy salts that revert to the non-enhanced form in aqueous solution. In U.S. Pat. No. 5,955,065, there are described anhydrous antiperspirant compositions that include a suspended antiperspirant salt, such as an enhanced efficacy aluminum-zirconium tetrachlorohydrex-gly (with peak 4:3>0.5), and a water soluble calcium salt, typically in an amount of about 0.5% to 15%.
In U.S. Pat. No. 5,804,203, there are described topical compositions that contain an irritant ingredient (e.g., organic alcohol, carboxylic acid, keto acid, peroxide, etc.), an anti-irritant divalent strontium cation, and a cosmetic or therapeutic active ingredient. The strontium cation is said to reduce skin irritation that would otherwise result from the irritant ingredient. Example 11 illustrates an antiperspirant composition that includes aluminum chlorohydrate, ethanol and strontium nitrate. This composition does not include an amino acid or a zirconium salt. In U.S. Pat. No. 5,958,436, there are described topical compositions that contain an irritant ingredient (e.g., organic alcohol, carboxylic acid, keto acid, peroxide, etc.), and an anti-irritant divalent calcium cation. The calcium cation is said to reduce skin irritation that would otherwise result from the irritant ingredient.
In U.S. Pat. No. 5,788,956, it is suggested that perspiration can be controlled by topically applying a substance P antagonist. Various substance P antagonists are disclosed including peptide and non-peptide nitrogenous derivatives and salts of monovalent, divalent and trivalent cations. The latter includes strontium, magnesium, cobalt, nickel, manganese, barium, etc. Examples 1, 3 and 4 of the patent disclose compositions containing strontium chloride or strontium nitrate. However, the patent does not provide any sweat reduction data for the exemplified compositions. In contrast to the suggestion in this patent, the present applicant found that a clear gel product containing 5% strontium nitrate does not provide any measurable sweat reduction (see Example 1, test product “Comp.1”, infra).
Recently, a new type of enhanced efficacy aluminum-zirconium antiperspirant salt is described in U.S. Pat. No. 6,436,381, which is incorporated herein by reference. These salts, when analyzed by HPLC as a 10% aqueous solution using conditions capable of resolving the aluminum into at least four successive peaks (conveniently labeled peaks 2 to 5), exhibit an HPLC peak 5 area of at least 33% or more, preferably at least 45%, based on the total area of HPLC peaks 2 to 5. That is, the salts have a high peak 5 Al content. These salts also typically have a low metal (Al+Zr) to chloride (or anion) ratio, for example, between 0.90 and 1.00. These high peak 5 enhanced efficacy salts, hereinafter referred to as “E5AZCH”, may have greater efficacy, in some applications, than the previously known enhanced efficacy aluminum-zirconium salts with high peak 4 content (i.e., peak 4>30% or peak 4:3>0.7 and peak 5<25%).
It would be highly desirable to provide enhanced efficacy antiperspirant compositions with superior efficacy, in particular, with higher efficacy than is currently obtained with the aforementioned E5AZCH salts.